1. Field of the Invention
The present invention relates to a wire bonding apparatus and, in particular, to a wire bonding apparatus having a distinctive wire clamp mechanism (device) for performing wire cutting/clamping in a wire bonding process.
2. Description of the Related Art
A wire clamp mechanism provided in a conventional wire bonding apparatus includes a stationary side wire clamp portion fixed to a bonding arm, a movable side wire clamp portion arranged in a scissors-like fashion with respect to the stationary side wire clamp portion and adapted to swing using one point as a fulcrum, and a clamp VCM (voice coil motor) connected to the movable side wire clamp portion and adapted to drive the movable side wire clamp portion.
The wire clamp device of this conventional wire bonding apparatus will be described in detail with reference to FIGS. 1 and 2. FIG. 1 is a top view showing an example of the wire clamp device provided in the conventional wire bonding apparatus, and FIG. 2 is a side view thereof. FIG. 3 is a diagram illustrating a wire bonding sequence.
As shown in FIGS. 1 and 2, in the conventional wire bonding apparatus, an X-Y stage 30 composed of an X-axis stage 1 and a Y-axis stage 2 are provided on a bonding apparatus base 14, and a bonding arm 4 is provided on a bonding head 3 secured to the X-Y stage 30. Then, the bonding arm 4 holds a horn 5 serving as a bonding tool, and a capillary 6 is secured to the forward end of the horn 5.
A gold wire 9 is passed through the capillary 6, and the gold wire 9 is held between a stationary wire gripping part 8 of stationary side wire clamp portion 7a and a movable wire gripping part 10 of a movable side wire clamp portion 7b at a position above the capillary 6. A coil 23 of a clamp VCM is connected to the movable side wire clamp portion 7b, and the coil 23 causes the movable side wire clamp portion 7b to swing on a fulcrum 15 to hold the gold wire 9 with the stationary side wire clamp portion 7a. Further the bonding arm 4 on which the wire clamp device is mounted swings at high speed around a bonding arm swinging shaft 13.
FIG. 3 shows the wire bonding sequence of the wire bonding apparatus. In FIG. 3, the horizontal axis indicates time, and the vertical axis indicates a height of the capillary 6 in the Z-axis direction.
First, in a state in which the gold wire 9 passed through the capillary 6 is not gripped by the wire clamp device, the Z-direction rotation portion including the wire clamp device and the bonding capillary 6 is lowered at a high speed (a). Further, search on the bonding part is executed in (b), US junction is effected in (c), a predetermined amount of the gold wire 9 is reversed in (d), loop-up is effected in (e), and then loop-down is effected in (f).
Next, a second search is executed in (g), and a second bonding (US junction) is effected in (h). Subsequently, feed-up is effected in (i), and, in a state in which the gold wire 9 is gripped by the driving of the clamping VCM movable coil 23, a high-speed ascent is effected by the driving of the Z-axis VCM 23 in (j). After cutting the gold wire 9 connected at the second bonding point, sparking is performed and releasing the wire clamp device, and the gold ball due to the sparking is raised in (k). That is, in wire clamping, when second bonding has been completed (h) and feed-up operation has been completed (i), a clamp VCM coil 23 is driven to hold the gold wire 9, and ascent is effected in that state, thereby cutting the gold wire 9 connected at the second bonding point (j).
In the conventional bonding apparatus constructed as described above, the bonding arm 4 swings around the bonding arm swinging shaft 13 which extends horizontally, at high speed to perform wire bonding at high speed. To realize a high-speed swinging of the Z-axis (vertical direction), it is necessary to reduce the weight of the wire clamp device and to reduce inertia thereof around the swinging shaft. In the conventional wire clamp device, however, an actuator for driving the movable side wire clamp portion 7b of the wire clamp device is mounted on the bonding arm 4, so that it is difficult to achieve a reduction in the total weight and in the total inertia of the bonding arm 4 including the wire clamp device.
The present invention has been made in view of the above problem in the prior art. It is a main object of the present invention to provide a wire bonding apparatus, which realizes a reduction in the weight and inertia of a wire clamp section applied to the bonding arm, thereby allowing a high-speed swinging of the Z-axis.
To achieve the above object, according to the present invention, there is provided a wire bonding apparatus including an X-Y stage composed of an X stage and a Y stage moving, horizontally, X- and Y-directions, respectively, a swinging shaft fixed onto the X-Y stage, a bonding arm swinging in the Z-axis direction (vertical direction) perpendicular to the X- and Y-directions, around the swinging shaft, a pair of wire clamp portions gripping a bonding wire, and an actuator for driving the pair of wire clamp portions, wherein at least a part of the actuator and the wire clamp portions is separated from the bonding arm portion and fixed onto the X-Y stage. Favorably, a bonding head is fixed onto the X-Y stage and the part of the actuator and the wire clamp portions is fixed to the bonding head.
Further, the wire bonding apparatus may be constructed such that the entire actuator is separated from the bonding arm and fixed onto the X-Y stage.
Moreover, the wire bonding apparatus may be constructed such that the actuator is composed of a stationary side actuator portion and a movable side actuator portion movable along the stationary side actuator portion, and the stationary side actuator portion is separated from the bonding arm portion and fixed onto the X-Y stage, favorably, fixed onto the X-Y stage via a bonding head which is fixedly mounted on the X-Y stage.
Furthermore, the wire bonding apparatus may be constructed such that the actuator is connected to the X-Y stage by an elastic member, moves integrally with the bonding arm only when gripping the bonding wire, and is separated from the bonding arm when not gripping the bonding wire.
Still more, the wire bonding apparatus may be constructed such that the wire clamp portions are connected to the X-Y stage by an elastic member, move integrally with the bonding arm only when gripping the bonding wire, and are separated from the bonding arm portion when not gripping the bonding wire.
Further still, the wire bonding apparatus maybe constructed such that a protrusion equipped with a freely rolling ball is provided in the wire clamp side end portion of the actuator, and wherein when the bonding arm swings in the Z-axis direction, the ball provided on the protrusion abuts the wire clamp portion while rolling to pressurize the wire clamp portion.
Yet further, the wire bonding apparatus may be constructed such that the actuator is formed so as to be movable also in the Z-axis direction, and wherein when the bonding arm swings in the Z-axis direction, the wire clamp portion and at least a part of the actuator move together while in contact with each other.
Still moreover, the wire bonding apparatus may be constructed such that the movable side actuator portion is formed as a plate extending in the Z-axis direction, and wherein when the bonding arm swings in the Z-axis direction, the stationary side actuator portion pressurizes the wire clamp portion while deviating in the Z-axis direction.
Yet moreover, the wire bonding apparatus maybe constructed so as to include a driving force transmission means provided between the actuator and the wire clamp and separated from the bonding arm, wherein the pressurizing force of the actuator is transmitted to the wire clamp portion through the driving force transmission means.
Still furthermore, the wire bonding apparatus may be constructed such that the actuator includes one of a VCM, a linear motor, an electrostrictive element, and a magnetostrictive element.
Thus, in accordance with the present invention, at least a part of the wire clamp portion and a section of the actuator for driving the wire clamp portion or the driving force transmitting means for transmitting the reciprocal movement of the actuator to the wire clamp portion is mounted outside the bonding arm to achieve a reduction in the total weight and total inertia of the bonding arm, making it possible to realize a high-speed Z-axis swinging of the bonding arm.